An audio circuit I found online and have been playing with has an odd
design (to me).

It's op-amp based running off a (separate) +/-15v supply.

There are on board caps across the supply, which is common enough. 10 and
0.1uF in parallel. But instead of going to ground, they are wired across
the +/-15v. Does that do the job as well? Or serves a different purpose?

--
*He who laughs last, thinks slowest.

Dave Plowman London SW
To e-mail, change noise into sound.

On 14/06/2021 11:07, Dave Plowman (News) wrote:
An audio circuit I found online and have been playing with has an odd
design (to me).

It's op-amp based running off a (separate) +/-15v supply.

There are on board caps across the supply, which is common enough. 10 and
0.1uF in parallel. But instead of going to ground, they are wired across
the +/-15v. Does that do the job as well? Or serves a different purpose?


It is probably ok - and it does save two components. Can you post a link
to the cct?

PA

"Dave Plowman (News)" wrote:
An audio circuit I found online and have been playing with has an odd
design (to me).

It's op-amp based running off a (separate) +/-15v supply.

There are on board caps across the supply, which is common enough. 10 and
0.1uF in parallel. But instead of going to ground, they are wired across
the +/-15v. Does that do the job as well? Or serves a different purpose?

Is the opamp powered off those +/- rails? In dual-rail circuits often power
is drawn from the + and - rails, and the GND rail acts as a handy halfway
reference point but doesn't actually source/sink much current. That means
switching transients are taking gulps of current between + and -, and so
decoupling caps are placed between + and - to provide them.

If instead of +/-15v you thought of the circuit as 0/+30v with a PNP/NPN
stack of transistors between +30v and 0v you might see that even if there's
a +15v wire it's largely irrelevant as most of the current is going through
the transistor pair.

Theo

On 14/06/2021 11:07, Dave Plowman (News) wrote:
An audio circuit I found online and have been playing with has an odd
design (to me).

It's op-amp based running off a (separate) +/-15v supply.

There are on board caps across the supply, which is common enough. 10 and
0.1uF in parallel. But instead of going to ground, they are wired across
the +/-15v. Does that do the job as well? Or serves a different purpose?

I would say it is normal for 0V to be treated as ground and all supply
decoupling off that.

I can perhaps understand an instance where you might not want to impose
power supply noise/switch/ripple current on the ground rail. It depends
on the nature of the power supply.

In article ,
Fredxx wrote:
On 14/06/2021 11:07, Dave Plowman (News) wrote:
An audio circuit I found online and have been playing with has an odd
design (to me).

It's op-amp based running off a (separate) +/-15v supply.

There are on board caps across the supply, which is common enough. 10 and
0.1uF in parallel. But instead of going to ground, they are wired across
the +/-15v. Does that do the job as well? Or serves a different purpose?

I would say it is normal for 0V to be treated as ground and all supply
decoupling off that.

I can perhaps understand an instance where you might not want to impose
power supply noise/switch/ripple current on the ground rail. It depends
on the nature of the power supply.


Thanks for conflicting replies chaps. ;-)

The PS shown is a conventional transformer type with a regulator for each
rail and conventional smoothing.

The circuit suggests high quality op-amps and caps (on the audio side) so
I doubt it's just to save component count.

--
*Acupuncture is a jab well done*

Dave Plowman London SW
To e-mail, change noise into sound.

In article ,
Theo wrote:
"Dave Plowman (News)" wrote:
An audio circuit I found online and have been playing with has an odd
design (to me).

It's op-amp based running off a (separate) +/-15v supply.

There are on board caps across the supply, which is common enough. 10
and 0.1uF in parallel. But instead of going to ground, they are wired
across the +/-15v. Does that do the job as well? Or serves a different
purpose?

Is the opamp powered off those +/- rails? In dual-rail circuits often
power is drawn from the + and - rails, and the GND rail acts as a handy
halfway reference point but doesn't actually source/sink much current.
That means switching transients are taking gulps of current between +
and -, and so decoupling caps are placed between + and - to provide them.

Yes. There are a total of 7 opamps. All powered +/- It is an audio
filtering device with unbalanced in and out so a good ground important.

If instead of +/-15v you thought of the circuit as 0/+30v with a PNP/NPN
stack of transistors between +30v and 0v you might see that even if
there's a +15v wire it's largely irrelevant as most of the current is
going through the transistor pair.

I can see that. Just odd I've never seen it used before.

--
*Succeed, in spite of management *

Dave Plowman London SW
To e-mail, change noise into sound.

"Dave Plowman (News)" wrote:
I can see that. Just odd I've never seen it used before.

FWIW it's not wrong to use separate capacitors V+ to 0 and 0 to V-, but
effectively what you have there is half the capacitance from V+ to V- and
double the ESR, so you're adding components to make it worse. It might make
sense where there are single-rail loads running between V+ and 0 - for
example digital logic, which are more the kind of thing decoupling
capacitance is intended for (high frequency switching loads rather than
general audio ripple).

Theo

On 14/06/2021 14:10, Dave Plowman (News) wrote:
In article ,
Fredxx wrote:
On 14/06/2021 11:07, Dave Plowman (News) wrote:
An audio circuit I found online and have been playing with has an odd
design (to me).

It's op-amp based running off a (separate) +/-15v supply.

There are on board caps across the supply, which is common enough. 10 and
0.1uF in parallel. But instead of going to ground, they are wired across
the +/-15v. Does that do the job as well? Or serves a different purpose?

I would say it is normal for 0V to be treated as ground and all supply
decoupling off that.

I can perhaps understand an instance where you might not want to impose
power supply noise/switch/ripple current on the ground rail. It depends
on the nature of the power supply.


Thanks for conflicting replies chaps. ;-)

It always "depends" on the detail. :-)

The PS shown is a conventional transformer type with a regulator for each
rail and conventional smoothing.

Are the 2 parallel caps associated with this 'conventional smoothing'?

The circuit suggests high quality op-amps and caps (on the audio side) so
I doubt it's just to save component count.

The only explanation I can thing of is the op-amps have very high power
supply rejection ratio and the idea is to minimise ground current.

Personally I would have used OV / GND as a PS common and had two caps.
There are ways of minimise the injection of PS noise currents.

Theo wrote:
"Dave Plowman (News)" wrote:
I can see that. Just odd I've never seen it used before.

FWIW it's not wrong to use separate capacitors V+ to 0 and 0 to V-, but
effectively what you have there is half the capacitance from V+ to V- and
double the ESR, so you're adding components to make it worse. It might make
sense where there are single-rail loads running between V+ and 0 - for
example digital logic, which are more the kind of thing decoupling
capacitance is intended for (high frequency switching loads rather than
general audio ripple).

Theo


One thing to be careful of, is this. If you're doing
this, the caps should not be dipped tantalum.

+15 ---+-----
|+
---
---
|
0 ---+-+---
|+
---
---
|
-15 -----+---

The problem with the circuit, is the behavior of
the power source. Any little bit of reverse bias
on a tantalum, sets it up to burst. And the epoxy dipped
ones will leave a PCB in a hurry. I had one ricochet
off a wall like a bullet. This only happened on my
bipolar wired setup (op amp test circuits), like the
one above, not on unipolar circuits.

If you're going to do that, ceramic (unpolarized)
and maybe an electrolytic will deal with a bit
of reverse bias, with less argument.

If you want to do bulk decoupling to reduce ripple
on the outside rails, maybe a tantalum would be
OK for this. But after my experiences, I don't
put tantalum in circuits any more. I still have
a few tantalums left, but they stay in that drawer
in the parts case.

+15 ---+---------+---
|+
---
---
|
0 ---+-+--- |
|
|
|
|
-15 -----+-------+----

The PSRR of the circuit, helps define how clean
your rails need to be. Linear regulators are
surprisingly noisy, and opamp PSRR isn't that
good at 1MHz. When you need absolutely the
lowest noise, supplying power can be a challenge.
A switcher at a fixed frequency, followed by
several stages of filtering circuits, may give lower
overall noise than the usage of linears. That's because,
by concentrating all the noise at the one frequency,
a more effective filter can be designed to "notch"
it out. You don't want variable-frequency switchers,
as the noise moves all over the place.

To start with then, running the project off a couple
nine volt batteries, and some good-sized electrolytics,
might be a way to go. Then there are no linears, and
it's just the noise spectrum of a battery (whatever that
is).

In the top diagram, the separate bypass on each side
of the bipolar supply, I never would have considered
that the rail polarity could reverse slightly at
shutdown. But the tantalums told me what was happening,
in a very effective way. When it goes with a "bang!",
it's like it is saying "you idiot, you reversed me!!!".
With safer capacitor types, you don't have to worry
quite as much.

Paul

On 14/06/2021 16:02, Fredxx wrote:
On 14/06/2021 14:10, Dave Plowman (News) wrote:
In article ,
Â*Â*Â* Fredxx wrote:
On 14/06/2021 11:07, Dave Plowman (News) wrote:
An audio circuit I found online and have been playing with has an odd
design (to me).

It's op-amp based running off a (separate) +/-15v supply.

There are on board caps across the supply, which is common enough.
10 and
0.1uF in parallel. But instead of going to ground, they are wired
across
the +/-15v. Does that do the job as well? Or serves a different
purpose?

I would say it is normal for 0V to be treated as ground and all supply
decoupling off that.

I can perhaps understand an instance where you might not want to impose
power supply noise/switch/ripple current on the ground rail. It depends
on the nature of the power supply.


Thanks for conflicting replies chaps. ;-)

It always "depends" on the detail. :-)

The PS shown is a conventional transformer type with a regulator for each
rail and conventional smoothing.

Are the 2 parallel caps associated with this 'conventional smoothing'?

The circuit suggests high quality op-amps and caps (on the audio side) so
I doubt it's just to save component count.

The only explanation I can thing of is the op-amps have very high power
supply rejection ratio and the idea is to minimise ground current.

Personally I would have used OV / GND as a PS common and had two caps.
There are ways of minimise the injection of PS noise currents.



Shame you can't point us to the circuits. Even with your extra notes,
above, there are still many questions arising - not least if your notes
are incorrect. (It does happen!)

Most Op Amps applications are inherently PSU-ripple insensitive.

PA

On 14/06/2021 17:55, Peter Able wrote:
On 14/06/2021 16:02, Fredxx wrote:
On 14/06/2021 14:10, Dave Plowman (News) wrote:
In article ,
Â*Â*Â* Fredxx wrote:
On 14/06/2021 11:07, Dave Plowman (News) wrote:
An audio circuit I found online and have been playing with has an odd
design (to me).

It's op-amp based running off a (separate) +/-15v supply.

There are on board caps across the supply, which is common enough.
10 and
0.1uF in parallel. But instead of going to ground, they are wired
across
the +/-15v. Does that do the job as well? Or serves a different
purpose?

I would say it is normal for 0V to be treated as ground and all supply
decoupling off that.

I can perhaps understand an instance where you might not want to impose
power supply noise/switch/ripple current on the ground rail. It depends
on the nature of the power supply.


Thanks for conflicting replies chaps. ;-)

It always "depends" on the detail. :-)

The PS shown is a conventional transformer type with a regulator for
each
rail and conventional smoothing.

Are the 2 parallel caps associated with this 'conventional smoothing'?

The circuit suggests high quality op-amps and caps (on the audio
side) so
I doubt it's just to save component count.

The only explanation I can thing of is the op-amps have very high
power supply rejection ratio and the idea is to minimise ground current.

Personally I would have used OV / GND as a PS common and had two caps.
There are ways of minimise the injection of PS noise currents.



Shame you can't point us to the circuits.Â* Even with your extra notes,
above, there are still many questions arising - not least if your notes
are incorrect. (It does happen!)

Most Op Amps applications are inherently PSU-ripple insensitive.

I managed to find this article, which features different power supply
decoupling and some reasoning behind the choices.
https://sound-au.com/dwopa.htm

Shame you can't point us to the circuits. Even with your extra notes,
above, there are still many questions arising - not least if your notes
are incorrect. (It does happen!)

Most Op Amps applications are inherently PSU-ripple insensitive.

They are a design from Elliot Sound Products. But the published schematic
doesn't show the supply rail side of the design. You have to buy the PCB
to see it.

--
*IF A TURTLE DOESN'T HAVE A SHELL, IS HE HOMELESS OR NAKED?

Dave Plowman London SW
To e-mail, change noise into sound.

In article ,
Fredxx wrote:
I managed to find this article, which features different power supply
decoupling and some reasoning behind the choices.
https://sound-au.com/dwopa.htm

Now there's a thing. It's a design from ESP I'm referring to. ;-)

--
*I have never hated a man enough to give his diamonds back.

Dave Plowman London SW
To e-mail, change noise into sound.

Depends is the answer as always. Those will do something but surely there
have to be capacitors across each supply half?
I'm assuming that the 0v is in fact earth for the circuit. The only time I
saw capacitors in the manner you suggest was when the full supply was used
as it is as a separate supply to another circuit. One then has to be very
careful with your earth!
Small caps across split rails are common to stop RF pick up though, that is
all I have seen. What exactly is this circuit doing? Normally if its audio
bespoke chips can be used that do not in themselves need split supplies.
Brian

--

This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...

Blind user, so no pictures please
Note this Signature is meaningless.!
"Dave Plowman (News)" wrote in message
...
An audio circuit I found online and have been playing with has an odd
design (to me).

It's op-amp based running off a (separate) +/-15v supply.

There are on board caps across the supply, which is common enough. 10 and
0.1uF in parallel. But instead of going to ground, they are wired across
the +/-15v. Does that do the job as well? Or serves a different purpose?

--
*He who laughs last, thinks slowest.

Dave Plowman London SW
To e-mail, change noise into sound.

I had a lot of trouble with some of Uncle Clive Sinclairs monolithic power
amps that operated in a bridge config, so the speaker was not really
earthed at either end. Worked great until one of power op amps, for in
effect that was what they were, popped its clogs and cooked the speakers and
firied the other chip.



Those circuits used to pop up in car output stages as I recall.
Brian

--

This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...

Blind user, so no pictures please
Note this Signature is meaningless.!
"Theo" wrote in message
...
"Dave Plowman (News)" wrote:
I can see that. Just odd I've never seen it used before.

FWIW it's not wrong to use separate capacitors V+ to 0 and 0 to V-, but
effectively what you have there is half the capacitance from V+ to V- and
double the ESR, so you're adding components to make it worse. It might
make
sense where there are single-rail loads running between V+ and 0 - for
example digital logic, which are more the kind of thing decoupling
capacitance is intended for (high frequency switching loads rather than
general audio ripple).

Theo

On 15/06/2021 00:17, Dave Plowman (News) wrote:
Shame you can't point us to the circuits. Even with your extra notes,
above, there are still many questions arising - not least if your notes
are incorrect. (It does happen!)

Most Op Amps applications are inherently PSU-ripple insensitive.

They are a design from Elliot Sound Products. But the published schematic
doesn't show the supply rail side of the design. You have to buy the PCB
to see it.


Assuming that Fredxx has the right link, I think that you should take it
with a little pinch of salt. An article originated 2000, referring to a
50+ year old Op Amp design (great advance though it was) is the first
hint. Concerns about supply impedance at audio frequencies is another.
If the guy was writing about designing with Dynamic Memory, then he'd be
closer to the mark. A bit OTT for audio.

Incidentally, you attack power supply noise at the power supply. I
wonder if the last components in your proposed PSU are - electrolytic
and / or other capacitors across the outputs.

At least he isn't trying to argue that no semiconductor device will beat
a 12AX7 ;-}

PA

On 15/06/2021 00:23, Dave Plowman (News) wrote:
In article ,
Fredxx wrote:
I managed to find this article, which features different power supply
decoupling and some reasoning behind the choices.
https://sound-au.com/dwopa.htm

Now there's a thing. It's a design from ESP I'm referring to. ;-)

It's comforting to see not everything I say is drivel :-)

I do suggest it is more typical to decouple everything to ground rather
than +ve to -ve. And I was trying to think of a possible reason why this
configuration might be chosen and not simply to save a couple of components.

I suppose extra decoupling could always be added afterwards if there is
any PS noise or a perceived advantage. Without knowing more about the
power supply it is difficult to call.

On 15/06/2021 08:07, Brian Gaff (Sofa) wrote:
Depends is the answer as always. Those will do something but surely there
have to be capacitors across each supply half?
I'm assuming that the 0v is in fact earth for the circuit. The only time I
saw capacitors in the manner you suggest was when the full supply was used
as it is as a separate supply to another circuit. One then has to be very
careful with your earth!
Small caps across split rails are common to stop RF pick up though, that is
all I have seen. What exactly is this circuit doing? Normally if its audio
bespoke chips can be used that do not in themselves need split supplies.
Brian


A centre tapped transformer with a full bridge can provide a +ve and -ve
outputs, with either a single capacitor or two, as per:

https://www.tubecad.com/2018/02/10/F...r%20Supply.png

Since Dave said there were regulators, and I assume of the linear
variety, there will already be decoupling before these regulators.

Another reason for having two caps, and decoupling from +ve and -ve to
0V is that many regulators are unstable (and sing or create lots of
noise) and specify a certain capacitance with a certain ESR on their
output.

Without more details this is all lots of speculation.

On 15/06/2021 10:35, Peter Able wrote:
Assuming that Fredxx has the right link, I think that you should take it
with a little pinch of salt.Â* An article originated 2000, referring to a
50+ year old Op Amp design (great advance though it was) is the first
hint.

More than a hint, since transistorss weren't invented then let alone opanps

Concerns about supply impedance at audio frequencies is another.
If the guy was writing about designing with Dynamic Memory, then he'd be
closer to the mark.Â* A bit OTT for audio.

Incidentally, you attack power supply noise at the power supply.Â* I
wonder if the last components in your proposed PSU are - electrolytic
and / or other capacitors across the outputs.

But you attck nouse ON the power supply wherever its being generated

At least he isn't trying to argue that no semiconductor device will beat
a 12AX7 ;

In 1950, he would be correct

--
There is something fascinating about science. One gets such wholesale
returns of conjecture out of such a trifling investment of fact.

Mark Twain

In article ,
Peter Able wrote:
On 15/06/2021 00:17, Dave Plowman (News) wrote:
Shame you can't point us to the circuits. Even with your extra notes,
above, there are still many questions arising - not least if your notes
are incorrect. (It does happen!)

Most Op Amps applications are inherently PSU-ripple insensitive.

They are a design from Elliot Sound Products. But the published schematic
doesn't show the supply rail side of the design. You have to buy the PCB
to see it.


Assuming that Fredxx has the right link, I think that you should take it
with a little pinch of salt. An article originated 2000, referring to a
50+ year old Op Amp design (great advance though it was) is the first
hint. Concerns about supply impedance at audio frequencies is another.
If the guy was writing about designing with Dynamic Memory, then he'd be
closer to the mark. A bit OTT for audio.

I'd not read that article before.

Incidentally, you attack power supply noise at the power supply. I
wonder if the last components in your proposed PSU are - electrolytic
and / or other capacitors across the outputs.

The PS shown is fairly typical of a regulated analogue type designed for
use with audio circuits.

I generally fit 0.1uF ceramic close to each IC between each of the power
supply rails and ground.

At least he isn't trying to argue that no semiconductor device will beat
a 12AX7 ;-}

PA

--
*Oh, what a tangled website we weave when first we practice *

Dave Plowman London SW
To e-mail, change noise into sound.

On 15 Jun 2021 at 13:36:27 BST, "The Natural Philosopher"
wrote:

On 15/06/2021 10:35, Peter Able wrote:
Assuming that Fredxx has the right link, I think that you should take it
with a little pinch of salt.Â* An article originated 2000, referring to a
50+ year old Op Amp design (great advance though it was) is the first
hint.

More than a hint, since transistorss weren't invented then let alone opanps

Concerns about supply impedance at audio frequencies is another.

The paradox is explained when you note that the article is 20 years old and
the 741 50+ years old *now*.




If the guy was writing about designing with Dynamic Memory, then he'd be
closer to the mark.Â* A bit OTT for audio.

Incidentally, you attack power supply noise at the power supply.Â* I
wonder if the last components in your proposed PSU are - electrolytic
and / or other capacitors across the outputs.

But you attck nouse ON the power supply wherever its being generated

At least he isn't trying to argue that no semiconductor device will beat
a 12AX7 ;

In 1950, he would be correct


--
Roger Hayter

On 15 Jun 2021 at 15:00:50 BST, "Roger Hayter" wrote:

On 15 Jun 2021 at 13:36:27 BST, "The Natural Philosopher"
wrote:

On 15/06/2021 10:35, Peter Able wrote:
Assuming that Fredxx has the right link, I think that you should take it
with a little pinch of salt.Â* An article originated 2000, referring to a
50+ year old Op Amp design (great advance though it was) is the first
hint.

More than a hint, since transistorss weren't invented then let alone opanps

Concerns about supply impedance at audio frequencies is another.

The paradox is explained when you note that the article is 20 years old and
the 741 50+ years old *now*.




If the guy was writing about designing with Dynamic Memory, then he'd be
closer to the mark.Â* A bit OTT for audio.

Incidentally, you attack power supply noise at the power supply.Â* I
wonder if the last components in your proposed PSU are - electrolytic
and / or other capacitors across the outputs.

But you attck nouse ON the power supply wherever its being generated

At least he isn't trying to argue that no semiconductor device will beat
a 12AX7 ;

In 1950, he would be correct

No, I don't know where that 20 years went either!

--
Roger Hayter

On 15/06/2021 15:00, Roger Hayter wrote:
On 15 Jun 2021 at 13:36:27 BST, "The Natural Philosopher"
wrote:

On 15/06/2021 10:35, Peter Able wrote:
Assuming that Fredxx has the right link, I think that you should take it
with a little pinch of salt.Â* An article originated 2000, referring to a
50+ year old Op Amp design (great advance though it was) is the first
hint.

More than a hint, since transistorss weren't invented then let alone opanps

Concerns about supply impedance at audio frequencies is another.

The paradox is explained when you note that the article is 20 years old and
the 741 50+ years old *now*.

Which all but NatPhil seem to have understood. I'll try to write more
inclusively next time ;-}



If the guy was writing about designing with Dynamic Memory, then he'd be
closer to the mark.Â* A bit OTT for audio.

Incidentally, you attack power supply noise at the power supply.Â* I
wonder if the last components in your proposed PSU are - electrolytic
and / or other capacitors across the outputs.

But you attck nouse ON the power supply wherever its being generated

At least he isn't trying to argue that no semiconductor device will beat
a 12AX7 ;

In 1950, he would be correct



PA

On 15/06/2021 18:25, Fredxx wrote:

I'm struggling to see this phrase. A word search finds 3 'year's as part
of 2 'many years" and one "over the years". A search of '50' finds 4,
none of which pertain to time.

That is because it is not a quote. When I quote I follow the convention
of quotation marks - so I might have quoted such technical expressions
as "rubbish", "more rubbish", "unmitigated drivel", "frauds and charlatans".

And you?

PA

On 15/06/2021 13:45, Dave Plowman (News) wrote:
In article ,
Peter Able wrote:
On 15/06/2021 00:17, Dave Plowman (News) wrote:
Shame you can't point us to the circuits. Even with your extra notes,
above, there are still many questions arising - not least if your notes
are incorrect. (It does happen!)

Most Op Amps applications are inherently PSU-ripple insensitive.

They are a design from Elliot Sound Products. But the published schematic
doesn't show the supply rail side of the design. You have to buy the PCB
to see it.


Assuming that Fredxx has the right link, I think that you should take it
with a little pinch of salt. An article originated 2000, referring to a
50+ year old Op Amp design (great advance though it was) is the first
hint. Concerns about supply impedance at audio frequencies is another.
If the guy was writing about designing with Dynamic Memory, then he'd be
closer to the mark. A bit OTT for audio.

I'd not read that article before.

Incidentally, you attack power supply noise at the power supply. I
wonder if the last components in your proposed PSU are - electrolytic
and / or other capacitors across the outputs.

The PS shown is fairly typical of a regulated analogue type designed for
use with audio circuits.

And it has some C at the LV output(s)?

PA

PS those of us in engineering at that time were so grateful to see the
741 kick the 709 out of designs.

On 15/06/2021 18:44, Fredxx wrote:
On 15/06/2021 18:25, Fredxx wrote:
On 15/06/2021 10:35, Peter Able wrote:
On 15/06/2021 00:17, Dave Plowman (News) wrote:
Shame you can't point us to the circuits.Â* Even with your extra notes,
above, there are still many questions arising - not least if your
notes
are incorrect. (It does happen!)

Most Op Amps applications are inherently PSU-ripple insensitive.

They are a design from Elliot Sound Products. But the published
schematic
doesn't show the supply rail side of the design. You have to buy the
PCB
to see it.


Assuming that Fredxx has the right link, I think that you should take
it with a little pinch of salt.Â* An article originated 2000,
referring to a 50+ year old Op Amp design (great advance though it
was) is the first hint.

I'm struggling to see this phrase. A word search finds 3 'year's as
part of 2 'many years" and one "over the years". A search of '50'
finds 4, none of which pertain to time.

FAOD the article was revamped in 2021. Perhaps they frequent this
newsgroup and updated it in the past day or so? Rod? No, he claims to
be a chemist.

Perhaps Rod Speed is AKA Rod Elliott?


Or Russ Andrews !

PA

On 15/06/2021 18:37, Fredxx wrote:
On 15/06/2021 13:36, The Natural Philosopher wrote:
On 15/06/2021 10:35, Peter Able wrote:

At least he isn't trying to argue that no semiconductor device will
beat a 12AX7 ;

In 1950, he would be correct

I'm sure some transistors in Bell Labs in 1950 would have some
characteristic that would beat a 12AX7. Size might be one, though the
first ones had a hefty package.

Hell, the 12AX7 was only 'invented' in 1946.
Â* https://en.wikipedia.org/wiki/12AX7


Indeed Bell Labs would have. Vis-a-vis perceived lifetimes, the 2N3055
is on its state pension by now - but still a useful device to have in
the junk box. Go back the same number years from the 12AX7's birth date
and you are back in Victorian times!

PA

On 15/06/2021 19:02, charles wrote:
In article ,
Fredxx wrote:
On 15/06/2021 13:36, The Natural Philosopher wrote:
On 15/06/2021 10:35, Peter Able wrote:
Assuming that Fredxx has the right link, I think that you should take
it with a little pinch of salt. An article originated 2000, referring
to a 50+ year old Op Amp design (great advance though it was) is the
first hint.

More than a hint, since transistorss weren't invented then let alone
opanps


we certainly had transistors when I was at school - late 1950s and my copy
of "Mullard Manual of Transistor Circuits in dated 1961. That's 60 years
aago.


We're obviously of a similar age. When I won a book prize at grammar
school I nominated that as the prize. The school was scandalised! "No
one has EVER been given a paperback book at Speech Day!!!!". The
compromise was that I choose a conventional book (a hardback Latin
dictionary), as well.

I still have both. You can guess which is the more thumbed !

PA

On 15/06/2021 10:35, Peter Able wrote:
On 15/06/2021 00:17, Dave Plowman (News) wrote:
Shame you can't point us to the circuits.Â* Even with your extra notes,
above, there are still many questions arising - not least if your notes
are incorrect. (It does happen!)

Most Op Amps applications are inherently PSU-ripple insensitive.

They are a design from Elliot Sound Products. But the published schematic
doesn't show the supply rail side of the design. You have to buy the PCB
to see it.


Assuming that Fredxx has the right link, I think that you should take it
with a little pinch of salt.Â* An article originated 2000, referring to a
50+ year old Op Amp design (great advance though it was) is the first
hint.

I'm struggling to see this phrase. A word search finds 3 'year's as part
of 2 'many years" and one "over the years". A search of '50' finds 4,
none of which pertain to time.

FAOD the article was revamped in 2021. Perhaps they frequent this
newsgroup and updated it in the past day or so? Rod? No, he claims to be
a chemist.

Concerns about supply impedance at audio frequencies is another.

Many op-amps are effective Class B outputs, where pulses in current
occur when the output is changing.

If the guy was writing about designing with Dynamic Memory, then he'd be
closer to the mark.

DRAM is relatively simple to decouple. There are models that predict
voltage dips and resonant behaviour for multiple decoupling capacitors
on power pins with multiple value.

A bit OTT for audio.

The design voltage ripply for DRAMS would be somewhat higher than levels
preferred for audio.

Incidentally, you attack power supply noise at the power supply.Â* I
wonder if the last components in your proposed PSU are - electrolytic
and / or other capacitors across the outputs.

What outputs? I would hope regulator outputs. It's normal to use a mix
of types, though high value ceramic is sometimes used alone.

At least he isn't trying to argue that no semiconductor device will beat
a 12AX7 ;-}

That would be difficult to argue. I note on some equipment the valve is
there for pure show, and while the heater is glowing all they are
producing is heat.

On 15/06/2021 13:36, The Natural Philosopher wrote:
On 15/06/2021 10:35, Peter Able wrote:
Assuming that Fredxx has the right link, I think that you should take
it with a little pinch of salt.Â* An article originated 2000, referring
to a 50+ year old Op Amp design (great advance though it was) is the
first hint.

More than a hint, since transistorss weren't invented then let alone opanps

From what I can read I can't see any reference to 50+ years and the
article was revamped in 2021.

BTW, the Transistor was invented in 1947.
https://en.wikipedia.org/wiki/History_of_the_transistor

It's perhaps ironic they were trying to fabricate a J-FET and that
Julius Lilienfeld is credited with the first patent on the FET in 1925.
https://en.wikipedia.org/wiki/Julius_Edgar_Lilienfeld

Concerns about supply impedance at audio frequencies is another.
If the guy was writing about designing with Dynamic Memory, then he'd
be closer to the mark.Â* A bit OTT for audio.

Incidentally, you attack power supply noise at the power supply.Â* I
wonder if the last components in your proposed PSU are - electrolytic
and / or other capacitors across the outputs.

But you attck nouse ON the power supply wherever its being generated

At least he isn't trying to argue that no semiconductor device will
beat a 12AX7 ;

In 1950, he would be correct

I'm sure some transistors in Bell Labs in 1950 would have some
characteristic that would beat a 12AX7. Size might be one, though the
first ones had a hefty package.

Hell, the 12AX7 was only 'invented' in 1946.
https://en.wikipedia.org/wiki/12AX7

On 15/06/2021 19:04, Fredxx wrote:
On 15/06/2021 17:52, Peter Able wrote:
On 15/06/2021 18:25, Fredxx wrote:

I'm struggling to see this phrase. A word search finds 3 'year's as
part of 2 'many years" and one "over the years". A search of '50'
finds 4, none of which pertain to time.

That is because it is not a quote.Â* When I quote I follow the
convention of quotation marks - so I might have quoted such technical
expressions as "rubbish", "more rubbish", "unmitigated drivel",
"frauds and charlatans".

And you?


I just don't get your point, "An article originated 2000, referring to a
50+ year old Op Amp design (great advance though it was) is the first
hint".

The uA741 is still in production, and the 741 is the ubiquitous op-amp.
Â* https://www.ti.com/lit/ds/symlink/ua741.pdf
"SLOS094G€“ NOVEMBER 1970 €“REVISED JANUARY 2018"

A bit like a 2N3055 is to a power bipolar npn transistor.

Referring to circuits that have survived the test of time should give
credibility to an article, not one that should be taken with a "pinch of
salt".

Please explain why this article should be taken "with a little pinch of
salt"?

We've both commented on the life of the 2N3055, so there's common ground
there.

The 741 was surpassed 40 years ago, the improvements made since being
absolutely relevant to this article.

The article's quality is not helped by its use of terminology such as
"rubbish", "more rubbish", "unmitigated drivel", "frauds and charlatans".

I've written extensively for the technical press - but never in terms of
obsolete components - or using such foolish expressions. Personally,
I'd steer well clear of those who do.

PA

On 15/06/2021 18:25, Fredxx wrote:
On 15/06/2021 10:35, Peter Able wrote:
On 15/06/2021 00:17, Dave Plowman (News) wrote:
Shame you can't point us to the circuits.Â* Even with your extra notes,
above, there are still many questions arising - not least if your notes
are incorrect. (It does happen!)

Most Op Amps applications are inherently PSU-ripple insensitive.

They are a design from Elliot Sound Products. But the published
schematic
doesn't show the supply rail side of the design. You have to buy the PCB
to see it.


Assuming that Fredxx has the right link, I think that you should take
it with a little pinch of salt.Â* An article originated 2000, referring
to a 50+ year old Op Amp design (great advance though it was) is the
first hint.

I'm struggling to see this phrase. A word search finds 3 'year's as part
of 2 'many years" and one "over the years". A search of '50' finds 4,
none of which pertain to time.

FAOD the article was revamped in 2021. Perhaps they frequent this
newsgroup and updated it in the past day or so? Rod? No, he claims to be
a chemist.

Perhaps Rod Speed is AKA Rod Elliott?

In article ,
Fredxx wrote:
On 15/06/2021 13:36, The Natural Philosopher wrote:
On 15/06/2021 10:35, Peter Able wrote:
Assuming that Fredxx has the right link, I think that you should take
it with a little pinch of salt. An article originated 2000, referring
to a 50+ year old Op Amp design (great advance though it was) is the
first hint.

More than a hint, since transistorss weren't invented then let alone
opanps


we certainly had transistors when I was at school - late 1950s and my copy
of "Mullard Manual of Transistor Circuits in dated 1961. That's 60 years
aago.

--
from KT24 in Surrey, England
"I'd rather die of exhaustion than die of boredom" Thomas Carlyle

On 15/06/2021 17:52, Peter Able wrote:
On 15/06/2021 18:25, Fredxx wrote:

I'm struggling to see this phrase. A word search finds 3 'year's as
part of 2 'many years" and one "over the years". A search of '50'
finds 4, none of which pertain to time.

That is because it is not a quote.Â* When I quote I follow the convention
of quotation marks - so I might have quoted such technical expressions
as "rubbish", "more rubbish", "unmitigated drivel", "frauds and
charlatans".

And you?


I just don't get your point, "An article originated 2000, referring to a
50+ year old Op Amp design (great advance though it was) is the first hint".

The uA741 is still in production, and the 741 is the ubiquitous op-amp.
https://www.ti.com/lit/ds/symlink/ua741.pdf
"SLOS094G€“ NOVEMBER 1970 €“REVISED JANUARY 2018"

A bit like a 2N3055 is to a power bipolar npn transistor.

Referring to circuits that have survived the test of time should give
credibility to an article, not one that should be taken with a "pinch of
salt".

Please explain why this article should be taken "with a little pinch of
salt"?

"Fredxx" wrote in message
...
On 15/06/2021 10:35, Peter Able wrote:
On 15/06/2021 00:17, Dave Plowman (News) wrote:
Shame you can't point us to the circuits. Even with your extra notes,
above, there are still many questions arising - not least if your notes
are incorrect. (It does happen!)

Most Op Amps applications are inherently PSU-ripple insensitive.

They are a design from Elliot Sound Products. But the published
schematic
doesn't show the supply rail side of the design. You have to buy the PCB
to see it.


Assuming that Fredxx has the right link, I think that you should take it
with a little pinch of salt. An article originated 2000, referring to a
50+ year old Op Amp design (great advance though it was) is the first
hint.

I'm struggling to see this phrase. A word search finds 3 'year's as part
of 2 'many years" and one "over the years". A search of '50' finds 4, none
of which pertain to time.

FAOD the article was revamped in 2021. Perhaps they frequent this
newsgroup and updated it in the past day or so?

Rod? No, he claims to be a chemist.

In fact my BSc is in chemistry but my post grad research degree
involved very sophisticated electronics and computing and
everything I did after that involved those too, including op amps
and digital stuff, discrete transistors with the first two DEC minis.

Concerns about supply impedance at audio frequencies is another.

Many op-amps are effective Class B outputs, where pulses in current occur
when the output is changing.

If the guy was writing about designing with Dynamic Memory, then he'd be
closer to the mark.

DRAM is relatively simple to decouple. There are models that predict
voltage dips and resonant behaviour for multiple decoupling capacitors on
power pins with multiple value.

A bit OTT for audio.

The design voltage ripply for DRAMS would be somewhat higher than levels
preferred for audio.

Incidentally, you attack power supply noise at the power supply. I
wonder if the last components in your proposed PSU are - electrolytic and
/ or other capacitors across the outputs.

What outputs? I would hope regulator outputs. It's normal to use a mix of
types, though high value ceramic is sometimes used alone.

At least he isn't trying to argue that no semiconductor device will beat
a 12AX7 ;-}

That would be difficult to argue. I note on some equipment the valve is
there for pure show, and while the heater is glowing all they are
producing is heat.

On Wed, 16 Jun 2021 04:54:05 +1000, cantankerous trolling geezer Rodent
Speed, the auto-contradicting senile sociopath, blabbered, again:


In fact my BSc is in chemistry but my post grad research degree
involved very sophisticated electronics and computing and
everything I did after that involved those too, including op amps
and digital stuff, discrete transistors with the first two DEC minis.

Don't forget to mention that you've been "involved in the design of a
computer OS", senile twit! LOL

--
Bill Wright addressing senile Ozzie cretin Rodent Speed:
"Well you make up a lot of stuff and it's total ******** most of it."
MID:

On 15/06/2021 18:38, Peter Able wrote:
On 15/06/2021 19:04, Fredxx wrote:
On 15/06/2021 17:52, Peter Able wrote:
On 15/06/2021 18:25, Fredxx wrote:

I'm struggling to see this phrase. A word search finds 3 'year's as
part of 2 'many years" and one "over the years". A search of '50'
finds 4, none of which pertain to time.

That is because it is not a quote.Â* When I quote I follow the
convention of quotation marks - so I might have quoted such technical
expressions as "rubbish", "more rubbish", "unmitigated drivel",
"frauds and charlatans".

And you?


I just don't get your point, "An article originated 2000, referring to
a 50+ year old Op Amp design (great advance though it was) is the
first hint".

The uA741 is still in production, and the 741 is the ubiquitous op-amp.
Â*Â* https://www.ti.com/lit/ds/symlink/ua741.pdf
"SLOS094G€“ NOVEMBER 1970 €“REVISED JANUARY 2018"

A bit like a 2N3055 is to a power bipolar npn transistor.

Referring to circuits that have survived the test of time should give
credibility to an article, not one that should be taken with a "pinch
of salt".

Please explain why this article should be taken "with a little pinch
of salt"?

We've both commented on the life of the 2N3055, so there's common ground
there.

The 741 was surpassed 40 years ago, the improvements made since being
absolutely relevant to this article.

The article's quality is not helped by its use of terminology such as
"rubbish", "more rubbish", "unmitigated drivel", "frauds and charlatans".

I see what you mean. Perhaps I take a greater issue with those
perpetuating myths, and brushed these phrases aside as being more
appropriate for Joe Public.

I've written extensively for the technical press - but never in terms of
obsolete components - or using such foolish expressions.Â* Personally,
I'd steer well clear of those who do.

They are not words I would choose either.

Peter Able wrote:
Incidentally, you attack power supply noise at the power supply. I
wonder if the last components in your proposed PSU are - electrolytic
and / or other capacitors across the outputs.

Nitpick: you attack noise at the source of the noise. Noise generated by
the power supply should be attacked at the power supply, as you say. Noise
generated on the power supply rails by other components should be attacked
close to where those components are.

The reason is that the power supply wiring has a certain impedance at the
frequency of consideration (due to 'parasitic' R/L/C). The further you go
from the source of the noise, the higher the impedance to reach it. And any
mitigation you put in is less able to work effectively because of that
impedance.

This is the reason for the folk wisdom of always fitting a 0.1uF capacitor
next to every IC - it has the minimum trace length and so the minimum
impedance to being able to damp current spikes from that IC switching.

(PDN analysis is a thing you have to do when the design is a bit more
critical, can avoid instability, and can also save you money on unnecessary
components. But folk wisdom gets you a long way if you're not manufacturing
in volume)

Theo

Peter Able wrote:
We're obviously of a similar age. When I won a book prize at grammar
school I nominated that as the prize. The school was scandalised! "No
one has EVER been given a paperback book at Speech Day!!!!". The
compromise was that I choose a conventional book (a hardback Latin
dictionary), as well.

:-)

My chosen prize was 'The Art of Electronics'. When I won the prize the next
year there was nothing else to top Horowitz and Hill, or at least that could
be found in the Charing Cross Road branch of Waterstones (the prize
unhelpfully provided in Waterstones vouchers, and Waterstones being truly
useless at technical books). So I had to settle for something less useful.

I still have both. You can guess which is the more thumbed !

Likewise

Theo

In article ,
Peter Able wrote:
The PS shown is fairly typical of a regulated analogue type designed for
use with audio circuits.

And it has some C at the LV output(s)?

Of course. Every decent regulated analogue PS for audio I've seen has C
across the rectifier and the output.

--
*I'm not a complete idiot, some parts are missing *

Dave Plowman London SW
To e-mail, change noise into sound.